Liposomes and related colloidal particulate systems have great promise as drug delivery systems, particularly for drugs with limited aqueous solubility. This approach has seen limited commercial application due to difficulties with stability and practical considerations related to dosing. Chemical degradation of liposome suspensions can be overcome for some applications by using synthetic nonionic surfactants to make niosomes. Physical degradation of liposome suspensions may be overcome by preparing the suspension at the point of use. To date, using niosomes has been difficult due to cumbersome preparative procedures. Preliminary results from this laboratory indicate that a novel formulation, referred to as "proniosomes," can provide better niosomes with less effort at the point of administration, in a form that is easier to dose and is probably more stable. In this proposed project, (1) preliminary work will be extended in order to identify a rational basis for these observations, (2) optimal formulations will be developed with model compounds to assess the limits of applicability, and (3) performance features will be compared to those of conventional preparations. If successful, this project will determine whether proniosomes are a suitable system for oral or topical delivery of drugs and establish a basis for future development using similar approaches to producing colloidal suspensions. The work will involve study of carrier properties (including study of particle size dependence, carrier solubility, carrier surface area), niosome composition, production conditions (anticipating scale-up), and some post-production processing (extrusion) using morphological evaluations and performance assays. It is expected that for high surface area carriers with good solubility, entrapment efficiency of more soluble drugs will be improved. The benefits of developing this methodology could extend to a variety of therapeutic areas and drug classes, and at the completion of this project, it will be known whether this is a feasible approach.